[Isp] [Fwd: Dynamics Happy Hour: TODAY, 3:30 pm]

[Terri Cantrell]

-------- Original Message --------
Subject: 	Dynamics Happy Hour: TODAY, 3:30 pm
Date: 	Wed, 08 Jul 2009 10:18:30 -0600
From: 	Russ Schumacher <rschumac at ucar.edu>
To: 	staff at mail.mmm.ucar.edu, visitor at mail.mmm.ucar.edu
CC: 	Lucas Harris <lharris4 at u.washington.edu>



---------------------------
Dynamics Happy Hour
3:30 pm, Wednesday 8 July
Room 2072 FL3
---------------------------

Title: On the Relative Performance of One-Way and Two-Way Grid Nesting

Speaker: Lucas Harris (Dept of Atmospheric Sciences, University of 
Washington)

Most mesoscale models can be run with either one-way (``parasitic'') or 
two-way (``interactive'') grid nesting. This paper presents results from 
a linear 1D shallow-water model and a 3D simulation of a multicell 
thunderstorm to determine whether the choice of nesting method can have 
a significant impact on the solution. Even for disturbances that are  
well-resolved on the coarse grid, it is found that one-way nesting can 
produce significantly more spurious reflection than two-way nesting when 
a disturbance exits the nested grid. The increased reflection in the  
one-way case is due to the difference in the phase speeds of the 
numerical solutions on the coarse and fine meshes, which can lead to 
accumulating phase differences between those solutions at the 
nested-grid boundary.  The superiority of two-way nesting proved robust 
to changes the boundary conditions imposed at the edge of the nested 
grid, including switching between simple interpolation and a Davies 
sponge layer at the boundary and varying the width of the sponge layer.





-- 
_________________________________________

Terri A. Cantrell
303-497-8281

http://www.isp.ucar.edu
Acting Administrator


NCAR
Integrated Science Program
P.O. Box 3000
FL1-2024
Boulder, CO 80307-3000

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